1. Field of the Invention
The invention relates to a method for Steckel mill rolling and finishing to produce hot-rolled flat steel products.
2. Brief Description of the Prior Art
Hot-rolled flat steel product is conventionally produced either by the use of a continuous hot strip mill or a reversing hot strip mill, known as a Steckel mill.
With a continuous hot strip mill, a heated transfer bar, such as a slab rolled on a roughing mill, is introduced to a series of in-line rolling stands, each having work rolls that produce a hot rolled flat product of the desired finished gauge. The flat product after completion of hot rolling is then subjected to cooling before coiling.
Although continuous hot strip mills are desired for high tonnage strip requirements and where the length of the rolling line is not of significance, for low tonnage applications, and where a relatively short rolling line is significant, the reversing hot rolling capability of the Steckel mill is of preferred use. In addition, a Steckel mill may be selectively used in the production of flat rolled products of thicker gauge, such as discrete plate rather than lighter gauge products such as sheet and strip produced in coil form.
A Steckel mill consists principally of a single reversing mill roll stand with a hot coiling furnace positioned on both the entry and exit side of the mill. The mill receives a transfer bar of approximately the same dimensions as that which would be used in the finishing roll stands of a continuous mill. During the rolling operation, the product is subjected to a sequential operation of coiling and uncoiling from the hot coiling furnaces of the Steckel mill until the desired reduction has been achieved.
The hot rolled product is then deflected onto a run out table where it is subjected to cooling prior to coiling. Alternately, in the production of thicker gauge flat rolled products, the transfer bar may be subjected to a series of reverse rolling processes through the Steckel mill with or without employing the hot coiling furnaces of the mill and the steel after cooling is produced as discrete plate rather than being coiled.
Where the length of the combined rolling and finishing line is significant, it is advantageous to reduce the size of the run-out table to less than 150 feet and yet complete the desired finishing operations, particularly cooling, to achieve the desired microstructure and physical and mechanical properties in the finished flat rolled product. This is not possible with conventional cooling practices employed in association with a Steckel mill having a run-out table this short.
It is accordingly an object of the present invention to provide a method for Steckel mill rolling and finishing of hot rolled flat steel products wherein the length of the finishing line necessary to achieve the required cooling may be made shorter than with conventional cooling practices used with both continuous hot strip mills and Steckel mills.